How do we know that Christ completed our salvation?

We can be certain that Christ completed our salvation because His declaration from the cross, 'It is finished,' affirms that He accomplished the full payment for sin and fulfilled all righteousness required by the law. This concept of tetelestai, meaning 'paid in full,' assures us that there remains no further work necessary for redemption. Christ was the perfect substitute who bore our iniquities, and as He laid down His life, He took upon Himself the wrath of God that was due to us. His resurrection further validates this work, as He rose victorious over sin and death, completing the salvation of His chosen people.